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Effect of Visible Light on the Recovery of Streptomyces Griseus Conidia from Ultra-violet Irradiation Injury.

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... k pred is the predicted photolysis rate constant of nucleic acid in viruses (cm 2 mJ −1 ), k pred,i is the predicted photolysis rate constant of the nucleic acid dimer or monomer i (TT, CT, TC, CC and C for DNA; and CC, UU, C and U for RNA) (cm 2 mJ −1 ), ε 254 is the molar absorption coefficient of i at 254 nm (M −1 cm −1 ), 254 is the quantum yield of a particular reaction at 254 nm (mol Eins −1 ), U 254 is the molar photon energy at 254 nm (4.72 × 10 5 J Eins −1 ), and N i is the number of i in the nucleic acid. It should be noted that dsDNA viruses may undergo repair in cells and can thus affect their UV 254 susceptibility ( Hijnen et al., 2006 ;Li et al., 2010 ;Stuchebrukhov, 2011 ;Kelner, 1949 ). It is infeasible to make quantitative estimation of the repaired genomes, thus a correction factor f is incorporated to simplify the situation ( Eq. 4 ). ...
... The DNA repair mechanism may partially account for this observation ( Hijnen et al., 2006 ). It has been reported that the photolyases in cells can repair the damaged DNA in the viruses ( Li et al., 2010 ;Stuchebrukhov, 2011 ;Yi and He, 2013 ), and this may result in recovery of viral infectivity ( Kelner, 1949 ). ...
Article
UV254 irradiation disinfection is a commonly used method to inactivate pathogenic viruses in water and wastewater treatment. Model prediction method can serve as a pre-screening tool to quickly estimate the effectiveness of UV254 irradiation on emerging or unculturable viruses. In this study, an improved prediction model was applied to estimate UV254 photolysis kinetics of viral genomes (kpred, genome) based on the genome sequences and their photoreactivity and to correlate with the experimental virus infectivity loss kinetics (kexp, infectivity). The UV254 inactivation data of 102 viruses (including 2 dsRNA, 65 ssRNA, 33 dsDNA and 2 ssDNA viruses) were collected from the published experimental data with kexp, infectivity ranging from 0.016 to 3.49 cm² mJ⁻¹. The model had fairly good performance in predicting the virus susceptibility to UV254 irradiation except dsRNA viruses (Pearson’s correlation coefficient = 0.64) and 70% of kpred, genome fell in the range of 1/2 to 2 times of kexp, infectivity. The positive deviation of the model often occurred for photoresistant viruses with low kexp, infectivity less than 0.20 cm² mJ⁻¹ (e.g., Adenovirus, Papovaviridae and Retroviridae). We also applied this model to predict the UV254 inactivation rate of SARS-CoV-2 (kpred, genome = 3.168 cm² mJ⁻¹) and a UV dose of 3 mJ cm⁻² seemed to be able to achieve a 2-log removal by conservative calculation using 1/2kpred, genome value. This prediction method can be used as a prescreening tool to assess the effectiveness of UV254 irradiation for emerging/unculturable viruses in water or wastewater treatment.
... A photoreactivation requires an additional exposure to near-UV and VIS radiation in the 350-450 nm range and results in degrading the formed CPDs by photolyases, a class of flavoproteins. This phenomenon was discovered by A. Kelner (1949), who observed the recovery of UVC-irradiated S. griseus under the visible light irradiation. The photoreactivation process by photolyase via electron-transfer mechanisms has been the topic of several comprehensive reviews (Thoma, 1999;Sinha and Häder, 2002;Weber, 2005;Liu et al., 2015). ...
Article
Development of the narrow-band mercury-free light sources, such as light emitting diodes (LEDs) and excilamps, has stimulated research on inactivation of pathogenic microorganisms by dual-wavelength light radiation. To date, dual-wavelength light radiation has emerged as an advanced tool for enhancing microbial inactivation in water in view of potential synergistic effect. This is the first review that aims at elucidating its mechanisms under dual-wavelength light exposure and surveying a body of related literature in terms of yes-or-no synergy. We have proposed three key inactivation mechanisms, which function in the estimated spectrum ranges I (190–254 nm), II (250–320 nm) and III (300–405 nm) and provide a synergistic effect when combined. These mechanisms involve proteins damage and DNA repair suppression (I), direct and indirect DNA damage (II) and generation of reactive oxygen species (ROS) by endogenous photosensitizers (III), such as porphyrins and flavins. A synergy under dual-wavelength light irradiation simultaneously or sequentially occurs if coupling two wavelengths of different ranges (I + II, I + III, II + III) in order to trigger different inactivation mechanisms. Recent advances of dual-wavelength light strategy in photodynamic therapy could be applied for water disinfection. They bring opportunities for applying the sources of near-UV and visible radiation and making the disinfection processes more energy- and cost-effective. From this standpoint, the synergistically efficient dual-wavelength combinations II + III and the combinations within the extended to 700 nm range III (near-UV + VIS) appear to be promising for developing novel advanced oxidation processes for disinfection of real turbid waters.
... The Watson-Crick faces of nucleobases are tucked in the interior of the DNA double helix, where they are largely inaccessible to solvent, shielded by Watson-Crick hydrogen bonding, and protected from endogenous and environmental agents that may cause various deleterious forms of alkylation damage (1)(2)(3). Yet alkylation damage to the Watson-Crick faces of nucleobases does occur in nature (4)(5)(6)(7)(8)(9) and can result in base modifications (Fig. 1A) that prevent Watson-Crick pairing and block or interfere with DNA replication. A variety of damage repair enzymes have evolved to address these lesions (7,10), which, if left unrepaired, can be highly cytotoxic and/or mutagenic (4,11). ...
Article
Full-text available
As the Watson-Crick faces of nucleobases are protected in double-stranded DNA (dsDNA), it is commonly assumed that deleterious alkylation damage to the Watson-Crick faces of nucleobases predominantly occurs when DNA becomes single-stranded during replication and transcription. However, damage to the Watson-Crick faces of nucleobases has been reported in dsDNA in vitro through mechanisms that are not understood. In addition, the extent of protection from methylation damage conferred by dsDNA relative to single-stranded DNA has not been quantified. Watson-Crick base-pairs in dsDNA exist in dynamic equilibrium with Hoogsteen base-pairs that expose the Watson-Crick faces of purine nucleobases to solvent. Whether this can influence the damage susceptibility of dsDNA remains unknown. Using dot-blot and primer extension assays, we measured the susceptibility of adenine-N1 to methylation by dimethyl sulfate (DMS) when in an A-T Watson-Crick versus Hoogsteen conformation. Relative to unpaired adenines in a bulge, Watson-Crick A-T base-pairs in dsDNA only conferred ~130-fold protection against adenine-N1 methylation and this protection was reduced to ~40-fold for A(syn)-T Hoogsteen base-pairs embedded in a DNA-drug complex. Our results indicate that Watson-Crick faces of nucleobases are accessible to alkylating agents in canonical dsDNA and that Hoogsteen base-pairs increase this accessibility. Given the higher abundance of dsDNA relative to ssDNA, these results suggest that dsDNA could be a substantial source of cytotoxic damage. The work establishes DMS probing as a method for characterizing A(syn)-T Hoogsteen base pairs in vitro and also lays the foundation for a sequencing approach to map A(syn)-T Hoogsteen and unpaired adenines genome-wide in vivo.
... By 1962 it was recognized that there was a repair process(es) acting on DNA and that this process acted in the dark and was distinct from a previously discovered light-dependent form of DNA repair: photoreactivation. The phenomenon of photoreactivation had been described in the late 1940s (Kelner 1949) and had even been subsequently accomplished in vitro (Wulff and Rupert 1962). It had been discovered that neighboring thymines in DNA were dimerized by UV radiation (Beukers and Berends 1960;Wulff and Fraenkel 1961) and that these dimers disappeared during photoreactivation (Wulff and Rupert 1962) (for review of this phenomenon see Friedberg 1997). ...
Article
The double stranded structure of DNA suggested a mechanism for replication. Overlooked was that it also served to maintain genome stability by providing a template for the repair of damage and mistakes in replication... The persistence of hereditary traits over many generations testifies to the stability of the genetic material. Although the Watson–Crick structure for DNA provided a simple and elegant mechanism for replication, some elementary calculations implied that mistakes due to tautomeric shifts would introduce too many errors to permit this stability. It seemed evident that some additional mechanism(s) to correct such errors must be required. This essay traces the early development of our understanding of such mechanisms. Their key feature is the cutting out of a section of the strand of DNA in which the errors or damage resided, and its replacement by a localized synthesis using the undamaged strand as a template. To the surprise of some of the founders of molecular biology, this understanding derives in large part from studies in radiation biology, a field then considered by many to be irrelevant to studies of gene structure and function. Furthermore, genetic studies suggesting mechanisms of mismatch correction were ignored for almost a decade by biochemists unacquainted or uneasy with the power of such analysis. The collective body of results shows that the double-stranded structure of DNA is critical not only for replication but also as a scaffold for the correction of errors and the removal of damage to DNA. As additional discoveries were made, it became clear that the mechanisms for the repair of damage were involved not only in maintaining the stability of the genetic material but also in a variety of biological phenomena for increasing diversity, from genetic recombination to the immune response.
... In 1949, a phenomenon named photoreactivation was independently discovered by Kelner (13) and by Dulbecco (14). Bacteria inactivated by UV irradiation could be reactivated when exposed to visible light (13); similarly, bacteriophages that had been UV-inactivated could be reactivated when infected bacteria were exposed to blue light (14). Rupert (15) demonstrated that photoreactivation is caused by an enzyme. ...
Article
Exposure of DNA to ultraviolet (UV) light from the Sun or from other sources causes formation of harmful and carcinogenic crosslinks between adjacent pyrimidine nucleobases, namely cyclobutane pyrimidine dimers and pyrimidine(6-4)pyrimidone photoproducts. Nature has developed unique flavoenzymes, called DNA photolyases, that utilize blue light, i.e. photons of lower energy than those of the damaging light, to repair these lesions. In this review, we focus on the chemically challenging repair of the (6-4) photoproducts by (6-4) photolyase and describe the major events along the quest for the reaction mechanisms, over the 20 years since the discovery of (6-4) photolyase. This article is protected by copyright. All rights reserved.
... Evidence of the simplest of DNA repair mechanisms emerged before DNA was even known to be the molecule carrying genetic information. Albert Kelner was trying to generate mutants of Streptomyces griseus using UV, in the hope of identifying antibiotics, when he noticed that fluorescent lights (of visible wavelengths) in the laboratory were responsible for discrepancies in the survival of colonies on agar plates (KELNER, 1949). Concomitantly, Renato Dulbecco too had noticed that agar plates of phageinfected bacteria stacked on his bench displayed different levels of survival after UV irradiation depending on their position in the stack (Dulbecco, 1949). ...
Conference Paper
A variety of DNA repair pathways operate in different cellular contexts to tackle a diversity of DNA lesions and maintain genome stability. Nucleotide excision repair (NER) recognises and removes a variety of helix-distorting lesions, operating via two pathways: a global-genome (GG-NER) and transcription-coupled (TC-NER) pathway. GG-NER repairs damage at any locus in the genome thus promoting genome stability by abrogating replication-mediated stress and mutagenesis. TCNER on the other hand is restricted to the template strand of actively transcribed genes and provides means to rapidly repair lesions that would otherwise impair transcription. Thus, TC-NER has seemingly evolved to not only maintain genome stability but sustain transcription by removal of RNA polymerase II (RNAPII)-stalling lesions. The two pathways differ in their mode of recognition of lesions while downstream repair steps of excision and DNA synthesis are mutual. GG-NER relies on XPC and UV-DDB that recognise and bind directly to lesions, initiating repair. TC-NER is initiated by a lesion-stalled RNAPII, which is recognised by Cockayne’s syndrome B (CSB) prompting recruitment of further repair factors. Mutations in CSB or CSA result in Cockayne’s syndrome, a disease characterised by photosensitivity, neurological deficiencies and progeria. UV-DDB and CSA reside in ubiquitin ligase complexes highlighting the importance of ubiquitylation in NER. The Svejstrup laboratory previously identified a ubiquitinbinding domain in CSB that was essential for its function as well as several CSAand UV-dependent ubiquitylation sites on CSB. Building on this work, I have developed a cell system exclusively expressing CSB mutants that are not ubiquitylated in response to UV-irradiation. I present evidence that ubiquitylation of CSB is necessary for the recovery of transcription and cell survival following UVirradiation. Inhibition of CSB ubiquitylation does not affect its recruitment to chromatin following UV, indicating it is a step downstream of the recognition and binding of a stalled RNAPII. These data support the hypothesis that CSB ubiquitylation is a vital step in TC-NER.
... This process is not dependent on a template 2 since the damage does not alter the sequence within which it occurs. Albert Kelner was the first scientist to observe that bacteria that have been seemingly inactivated by fatal doses of UV radiation suddenly revived upon exposure to visible blue light [1]. Aziz Sancar was fascinated by this and took it upon himself to understand the biochemistry behind this process. ...
Article
Full-text available
The 2015 Nobel Prize in Chemistry was awarded jointly to Tomas Lindahl, Paul Modrich and Aziz Sancar to honour their accomplishments in the field of DNA repair. Ever since the discovery of DNA structure and their importance in the storage of genetic information, questions about their stability became pertinent. A molecule which is crucial for the development and propagation of an organism must be closely monitored so that the genetic information is not corrupted. Thanks to the pioneering research work of Lindahl, Sancar, Modrich and their colleagues, we now have an holistic awareness of how DNA damage occurs and how the damage is rectified in bacteria as well as in higher organisms including human beings. A comprehensive understanding of DNA repair has proven crucial in the fight against cancer and other debilitating diseases.
... In this process, cell damage caused by UV light could be reversed by subsequent irradiation of the cells (Streptomyces griseus Conidia) with blue light. 84 In 1958, the photolyases were identified as the cause of the phenomenon of photo-reactivation in bacteria. 57,58,64 Photolyases are DNA repair enzymes that restore UV-light damaged DNA using visible light (Scheme 1B). ...
Article
Light has received increased attention for various chemical reactions but also in combination with biocatalytic reactions. Because currently only a few enzymatic reactions are known, which per se require light, most transformations involving light and a biocatalyst exploit light either for providing the cosubstrate or cofactor in an appropriate redox state for the biotransformation. In selected cases, a promiscuous activity of known enzymes in the presence of light could be induced. In other approaches, light-induced chemical reactions have been combined with a biocatalytic step, or light-induced biocatalytic reactions were combined with chemical reactions in a linear cascade. Finally, enzymes with a light switchable moiety have been investigated to turn off/on or tune the actual reaction. This Review gives an overview of the various approaches for using light in biocatalysis.
... UV light damages chromosomal DNA due to the formation of cyclobutane pyrimidine dimer (CPD) cross-links between adjacent thymidine nucleotides. Even short-duration UV irradiation, typically a few minutes, is highly potent in killing bacteria, provided that the cells are kept in the dark after the irradiation (7,8). Otherwise, light-dependent activity of photolyase decross-links CPD and prevents cell death on the recovery plate (9). ...
... Meanwhile, a paradoxical phenomenon is that, the UV-damaged DNA can be recovered by way of two repair mechanisms: photoreactivation by the enzyme photolyase that requires light of 330−480 nm and nucleotide excision repair (dark repair) that is light independent (Friedberg et al., 1995;Harm, 1980;Kelner, 1949;Oguma et al., 2001). This was even observed for non-resistant E.coli in the UVC-LED systems in our previous studies (Nyangaresi et al., 2018(Nyangaresi et al., , 2019b. ...
Article
Ultraviolet light emitting diode (UV-LED) has attracted extensive attention as a new technology to replace traditional mercury lamp for water disinfection. This study reported for the first time the application of UVC-LEDs in range of 200-280 nm for the treatment of two Gram-positive tetracycline resistant bacteria (TRB) from Bacillus species and their tetracycline resistant gene (TRG). The results showed that UVC-LEDs can inactivate TRB up to 5.7-log and inhibit TRG expression, especially at 268 nm. The required fluence was approximate to that of the referential non-resistant bacteria using the same UVC-LED, but far less than that of TRB using mercury lamp. After UVC-LED irradiation, photoreactivation was the dominant mechanism to repair TRB, just like non-resistant bacteria. But contrary to non-resistant bacteria, the regrowth ratio of TRB was remarkably high at 24 h since the end of the irradition, nevertheless the number of the regrown bacteria in the irradiated water was still less than that in the non-irradiated water. Whereas TRB restored resistance after repair even applying 268 nm at a fluence up to 46.08 mJ/cm2 (maximum in this study). This study highlights the merits of UVC-LED to effectively inactivate TRB in a prompt, energy-efficient and resistance-reducing way, while future study on TRB regrowth and resistance resilience is needed.
... To maintain genome integrity, organisms possess defense mechanisms against these photoproducts, including several DNA repair pathways (2,3). One powerful repair mechanism is photoreactivation, in which the harmful effects of UV radiation on organisms are reversed by concurrent or subsequent exposure to blue light (4,5). Photoreactivation is accomplished by DNA photolyase (6). ...
Article
Full-text available
Proteins of the cryptochrome/photolyase family (CPF) exhibit sequence and structural conservation, but their functions are divergent. Photolyase is a DNA repair enzyme that catalyzes the light-dependent repair of ultraviolet (UV)-induced photoproducts, whereas cryptochrome acts as a photoreceptor or circadian clock protein. Two types of DNA photolyase exist: CPD photolyase, which repairs cyclobutane pyrimidine dimers (CPDs), and 6-4 photolyase, which repairs 6-4 pyrimidine–pyrimidone photoproducts (6-4PPs). Although the Cry-DASH protein is classified as a cryptochrome, it also has light-dependent DNA repair activity. To determine the significance of the three light-dependent repair enzymes in recovering from solar UV-induced DNA damage at the organismal level, we generated mutants in each gene in medaka using the CRISPR genome editing technique. The light-dependent repair activity of the mutants was examined in vitro in cultured cells and in vivo in skin tissue. Light-dependent repair of CPD was lost in the CPD photolyase–deficient mutant, whereas weak repair activity against 6-4PPs persisted in the 6-4 photolyase–deficient mutant. These results suggest the existence of a heretofore unknown 6-4PP repair pathway, and thus improve our understanding of the mechanisms of defense against solar UV in vertebrates. This article is protected by copyright. All rights reserved.
... The Watson-Crick faces of nucleobases are tucked in the interior of the DNA double helix where they are largely inaccessible to solvent, shielded by Watson-Crick hydrogen bonding, and protected from endogenous and environmental agents that may cause various deleterious forms of alkylation damage (1)(2)(3). Yet alkylation damage to the Watson-Crick faces of nucleobases does occur in nature (4)(5)(6)(7)(8)(9) and can result in base modifications (Fig. 1A) that prevent Watson-Crick pairing and block or interfere with DNA replication. A variety of damage repair enzymes have evolved to address these lesions (7,10), which if left unrepaired, can be highly cytotoxic and/or mutagenic (4,11). ...
Preprint
As the Watson-Crick faces of nucleobases are protected in double-stranded DNA (dsDNA), it is commonly assumed that deleterious alkylation damage to the Watson-Crick faces of nucleobases predominantly occurs when DNA becomes single-stranded during replication and transcription. However, damage to the Watson-Crick faces of nucleobases has been reported in dsDNA in vitro through mechanisms that are not understood. In addition, the extent of protection from methylation damage conferred by dsDNA relative to single-stranded DNA (ssDNA) has not been quantified. Watson-Crick base-pairs in dsDNA exist in dynamic equilibrium with Hoogsteen base-pairs that expose the Watson-Crick faces of purine nucleobases to solvent. Whether this can influence the damage susceptibility of dsDNA remains unknown. Using dot-blot and primer extension assays, we measured the susceptibility of adenine-N1 to methylation by dimethyl sulfate (DMS) when in an A-T Watson-Crick versus Hoogsteen conformation. Relative to unpaired adenines in a bulge, Watson-Crick A-T base-pairs in dsDNA only conferred ~130-fold protection against adenine-N1 methylation and this protection was reduced to ~40-fold for A( syn )-T Hoogsteen base-pairs embedded in a DNA-drug complex. Our results indicate that Watson-Crick faces of nucleobases are accessible to alkylating agents in canonical dsDNA and that Hoogsteen base-pairs increase this accessibility. Given the higher abundance of dsDNA relative to ssDNA, these results suggest that dsDNA could be a substantial source of cytotoxic damage. The work establishes DMS probing as a method for characterizing A( syn )-T Hoogsteen base pairs in vitro andlays the foundation for a sequencing approach to map A( syn )-T Hoogsteen and unpaired adenines genome-wide in vivo .
... A second photolyase-related gene in Synechocystis (slr0854) is highly similar to class I photolyases and contributed to photoreactivation (Hitomi et al. 2000). Photoreactivation is the process that increases the survival rate of UV-treated cells or phages by visible light given simultaneously or immediately after UV exposure (Dulbecco 1949;Kelner 1949). These conclusions were confirmed by an independent study (Ng and Pakrasi 2001), which also showed that a slr0854/sll1629 (phrA/phrB) double mutant is slightly more sensitive against UV-B than the phrA single mutant, suggesting that phrB could have some photolyase activity. ...
Article
Full-text available
DASH (Drosophila, Arabidopsis, Synechocystis, human)-type cryptochromes (cry-DASHs) form one subclade of the cryptochrome/photolyase family (CPF). CPF members are flavoproteins that act as DNA-repair enzymes (DNA-photolyases), or as UV-A/blue light photoreceptors (cryptochromes). In mammals, cryptochromes are essential components of the circadian clock feed-back loop. Cry-DASHs are present in almost all major taxa and were initially considered as photoreceptors. Later studies demonstrated DNA-repair activity that was, however, restricted to UV-lesions in single-stranded DNA. Very recent studies, particularly on microbial organisms, substantiated photoreceptor functions of cry-DASHs suggesting that they could be transitions between photolyases and cryptochromes.
... Allowing the fruit to become exposed to visible wavelengths of light following treatment may have led to photoreversala phenomenon in which the effects of UV-C hormesis are negated by subsequent exposure to visible light (Kelner, 1949). It had previously been shown by Stevens et al. (1998b) that peaches, Prunus persica, exposed to 48 h of visible light following UV-C treatment no longer exhibited a reduction in brown rot lesions caused by Monilinia fructicola. ...
Article
Post-harvest hormetic treatment of mature green tomato fruit (Solanum lycopersicum cv. Mecano) with high intensity pulsed polychromatic light (HIPPL) significantly delayed ripening to levels comparable to those achieved using a conventional low intensity UV-C (LIUV) source. A 16 pulse HIPPL treatment reduced the ΔTCI (tomato colour index) by 50.1 % whilst treatment with a LIUV source led to a reduction of 43.1 %. Moreover, the 16 pulse treatment also induced disease resistance in the fruit to Botrytis cinerea with a 41.7 % reduction in disease progression compared to a 38.1 % reduction for the LIUV source. A single 16 pulse HIPPL treatment was found to significantly reduce disease progression on both mature green and ripe fruit with a 28.5 % reduction on ripe fruit in comparison to 13.4 % for the LIUV treatment. It is shown here that delayed ripening and disease resistance are local responses in side treated tomato fruit for both LIUV and HIPPL treatments. Finally, utilising a 16 pulse HIPPL treatment would reduce treatment times from 370 s for LIUV sources to 10 s per fruit - a 97.3 % reduction.
... In the beginning, there was "light repair" (1), also known as photolyase-and light-driven host cell reactivation (2). Immediately afterward, the so-called dark repair now known as excision repair, discovered by Richard Setlow (3), heralded a new expansive era in DNA repair research with many unique offshoots and intense areas of enquiry that culminated in the ultimate recognition and award of 2015 Nobel Prize in chemistry (4). ...
Article
Nucleotide excision repair (NER) eliminates a broad variety of helix-distorting DNA lesions that can otherwise cause genomic instability. NER comprises two distinct sub-pathways: global genomic NER (GG-NER) operating throughout the genome, and transcription-coupled NER (TC-NER) preferentially removing DNA lesions from transcribing DNA strands of transcriptionally active genes. Several NER factors undergo post-translational modifications, including ubiquitination, occurring swiftly and reversibly at DNA lesion sites. Accumulating evidence indicates that ubiquitination not only orchestrates the spatio-temporal recruitment of key protein factors to DNA lesion sites but also the productive assembly of NER preincision complex. This review will be restricted to the latest conceptual understanding of ubiquitin-mediated regulation of initial damage sensors of NER, i.e., DDB, XPC, RNAPII and CSB. We project hypothetical NER models in which ubiquitin-specific segregase, valosin-containing protein (VCP)/p97, plays an essential role in timely extraction of the congregated DNA damage sensors to functionally facilitate the DNA lesion elimination from the genome. This article is protected by copyright. All rights reserved.
... It has been known since the late 1940s that the viability of bacteria cells increases when UV-exposure is followed by visible light [60]. This phenomenon results mainly from the activity of photoreactive enzymes called photolyases [61]. ...
Article
Full-text available
Although solar light is indispensable for the functioning of plants, this environmental factor may also cause damage to living cells. Apart from the visible range, including wavelengths used in photosynthesis, the ultraviolet (UV) light present in solar irradiation reaches the Earth's surface. The high energy of UV causes damage to many cellular components, with DNA as one of the targets. Putting together the puzzle-like elements responsible for the repair of UV-induced DNA damage is of special importance in understanding how plants ensure the stability of their genomes between generations. In this review, we have presented the information on DNA damage produced under UV with a special focus on the pyrimidine dimers formed between the neighboring pyrimidines in a DNA strand. These dimers are highly mutagenic and cytotoxic, thus their repair is essential for the maintenance of suitable genetic information. In prokaryotic and eukaryotic cells, with the exception of placental mammals, this is achieved by means of highly efficient photorepair, dependent on blue/UVA light, which is performed by specialized enzymes known as photolyases. Photolyase properties, as well as their structure, specificity and action mechanism, have been briefly discussed in this paper. Additionally, the main gaps in our knowledge on the functioning of light repair in plant organelles, its regulation and its interaction between different DNA repair systems in plants have been highlighted.
... En effet en parallèle Albert Kelner et Renato Dulbecco constatent la multiplication des bactéries Streptomyces griseus ou des bactériophages (virus infectant les bactéries) suite à une exposition à la lumière blanche, malgré une inactivation préalable de ces dernières par rayonnements ultra-violets, cependant sans pouvoir apporter d'interprétations. 7,8 Ce phénomène a été expliqué par la suite par la prise en charge des dimères de pyrimidines créés au sein de l'ADN suite à l'exposition aux ultraviolets par une enzyme de réparation de type photolyase utilisant la lumière bleue comme source d'énergie. Le maintien de l'intégrité génomique est ainsi assuré par différentes voies de réparation spécifiques aux dommages. ...
Thesis
Dans le contexte de la chimiothérapie, la réparation de l’ADN réduit les dommages induits par les agents alkylants de l’ADN dont le témozolomide (TMZ), conduisant à la chimiorésistance. Une des voies principales de réparation de l’ADN est la voie par excision de base (BER) au sein de laquelle une enzyme clée, APE1 (endonucléase AP 1), clive les sites abasiques générés suite aux traitements par les agents alkylants et initie la réparation de la coupure simple-brin. Ce mécanisme représente une source majeure de chimiorésistance dans certains cancers. Plusieurs études ont ainsi validé la voie BER et plus particulièrement APE1 comme une cible importante dans le but d’améliorer l’efficacité des agents anticancéreux; pour ces raisons, de nombreux inhibiteurs d’APE1 ont été développés. Cependant, à la place d’une inhibition directe de l’enzyme, une stratégie alternative consiste à cibler le substrat de cette dernière : les sites abasiques. Les composés macrocycliques de type naphtalénophane ont montré la capacité à se lier fortement et sélectivement aux sites abasiques. Ce processus interfère avec la reconnaissance de ces derniers par APE1 et conduit in vitro à deux effets : l’inhibition du clivage enzymatique d’APE1 et le clivage du site AP par les macrocycles par un mécanisme différent de celui d'APE1, de type β-élimination. Ainsi, une nouvelle série de naphtalénophanes fonctionnalisés, composée de neuf nouveaux dérivés, a été synthétisée et étudiée. La plupart des macrocycles démontre la capacité à se lier fortement et sélectivement aux sites abasiques de l’ADN ainsi qu’à inhiber l’activité d’APE1 in vitro, avec des constantes d’inhibition s'étalant de 39 nM à 25 µM. De plus, l’activité d’inhibition d’APE1 par les ligands, caractérisée par les valeurs de Kı, a pu être corrélée avec leur affinité et leur sélectivité pour les sites abasiques. La structure moléculaire des macrocycles montre une forte influence sur l’activité de clivage de ces derniers pouvant conduire à une abolition ou à une très haute activité de clivage des sites abasiques. De façon intéressante, la formation d’un adduit covalent ADN – ligand avec un des macrocycles a été caractérisée. Enfin, l’activité biologique des naphtalénophanes sur la lignée cellulaire de glioblastome T98G résistante au TMZ a été étudiée. La plupart des ligands affiche une cytotoxicité élevée, avec des GI₅₀ de l’ordre du micromolaire. De plus, un remarquable effet synergique lors du traitement des cellules avec le TMZ et le MMS en combinaison avec un ligand (2,7-BisNP-O4Me) a été démontré. Ce macrocycle augmente également le nombre de sites abasiques et le nombre de coupures double-brins après un co-traitement cellulaire avec les agents alkylants suggérant ainsi l'inhibition d'APE1 attendue. Ces résultats mettent ainsi en évidence le fort intérêt thérapeutique de ce composé.
... The first evidence of photolyase activity goes back to the late 1940s, when the photoreactivation of UV-treated bacteria was observed on blue light exposure [35]. A decade later, the enzyme responsible for the photoreactivation was discovered [36]. ...
Article
Using light for biocatalysis is a relatively new and expanding research field. Due to the ever-increasing number of publications, this review highlights developments in the field of photobiocatalysis published in the past two years. We introduce the topic briefly and list most of the review articles appeared so far. Afterwards, we devote special attention to the most interesting and relevant key articles in the field of in vitro photobiocatalysis and briefly, we describe novel discoveries in photobiocatalytic cascades and in strict light-dependent enzymes. Finally, we outline developments in the next decade in the conclusions and future perspectives part.
... Les photolyases réparatrices des défauts CPD sont appelées photolyase CPD ou, pour Kelner découvrit en 1949 la photoréparation de cellules de Streptomyces griseus endommagées par UV[59]. Après excitation en lumière visible, il put observer le retour à un fonctionnement normal des cellules endommagées. ...
Thesis
i) Ce travail concerne la photoactivité de deux nouvelles flavoprotéines (OtPCF1 et OtCPF2) de l’algue verte Ostreococcus tauri, appartenant à la famille des cryptochromes et photolyases (CPF). Nous avons mis en évidence, dans les deux cas, un transfert d’électron ultrarapide (OtCPF1 : 390 fs ; OtCPF2 : 590 fs) après excitation du chromophore flavine adénine dinucléotide (FAD) sous forme oxydée. Nous avons caractérisé un résidu tryptophanecomme donneur d’électron. Nous expliquons les étapes ultérieures par des transferts d’électron le long d’une chaîne de trois résidus tryptophanes, conservés au sein des protéines CPF. Par ailleurs nous avons analysé le transfert d’énergie de la photoantenne de OtCPF2 vers FAD oxydée et réduite. Des analyses structurales, obtenues par modélisation par homologie, nous ont permis de rationaliser les résultats obtenus par spectroscopie transitoire ultrarapide.ii) Pour expliquer le photocycle ultrarapide observé pour OBIP, le photorécepteur supposé du protozoaire cilié Blepharisma japonicum, nous avons proposé un modèle original mettant en jeu un équilibre entre l’état localement excité du chromophore (Oxyblépharismine) en interaction par liaison hydrogène avec un résidu proche et un état à transfert de charge intermoléculaire. Nous avons également proposé que l’état signalant de la photophobie seraitla forme déprotonée du chromophore.
... In nature, microorganisms that are continuously exposed to UV radiation have developed different mechanisms to revert cell damage, including dark repairing mechanism [15] and photoreactivation (PHR) [16,17]. PHR was mentioned for the first time in the late 1940s [18], reporting that Streptomyces griseus was able to survive to several doses of UV light irradiation when stored under visible light conditions. Further works demonstrated the cellular basis of PHR and the molecular mechanism underlying it, opening a new field of research oriented to disclose the reaction mechanism of photolyases [19,20]. ...
Article
Photolyases are enzymes that repair DNA damage caused by solar radiation. Due to their photorepair potential, photolyases added in topical creams and used in medical treatments has allowed to reverse skin damage and prevent the development of different diseases, including actinic keratosis, premature photoaging and cancer. For this reason, research has been oriented to the study of new photolyases performing in extreme environments, where high doses of UV radiation may be a key factor for these enzymes to have perfected their photorepair potential. Generally, the extracted enzymes are first encapsulated and then added to the topical creams to increase their stability. However, other well consolidated immobilization methods are interesting strategies to be studied that may improve the biocatalyst performance. This review aims to go through the different Antarctic organisms that have exhibited photoreactivation activity, explaining the main mechanisms of photolyase DNA photorepair. The challenges of immobilizing these enzymes on porous and nanostructured supports is also discussed. The comparison of the most reported immobilization methods with respect to the structure of photolyases show that both covalent and ionic immobilization methods produced an increase in their stability. Moreover, the use of nanosized materials as photolyase support would permit the incorporation of the biocatalyst into the target cell, which is a technological requirement that photolyase based biocatalysts must fulfill.
... Since Kelner [1,2] reported in late 1940s that damaged DNA could be corrected, our knowledge about DNA damage and repair has increased exponentially [3]. DNA damage can be divided into 2 broad categories: base damage and strand breaks. ...
... Photoreactivation was first discovered in Streptomyces griseus (65). Hence, it came as a surprise that S. coelicolor A3(2) is incapable of enzymatic photoreactivation (41). ...
Article
Ultraviolettes Licht schädigt DNA, indem es zwei benachbarte Thymine in ein Thymin-Dimer umwandelt, das für den Organismus potenziell mutagen, karzinogen oder letal ist. Der Schaden wird durch Photolyase und Nukleotidexzisionsreparatur in E. coli und durch Nukleotidexzisionsreparatur im Menschen repariert. Die Arbeiten, die zu diesen Ergebnissen geführt haben, werden von A. Sancar in seinem Nobel-Aufsatz vorgestellt.
Article
Ultraviolet light damages DNA by converting two adjacent thymines into a thymine dimer which is potentially mutagenic, carcinogenic, or lethal to the organism. This damage is repaired by photolyase and the nucleotide excision repair system in E. coli by nucleotide excision repair in humans. The work leading to these results is presented by A. Sancar in his Nobel lecture.
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Die Bakterien sind die kleinsten autonomen Lebenseinheiten, die einen differenzierten Stoffwechselapparat unterhalten und in der Lage sind, sich selbständig zu vermehren. Für den Strahlenbiologen bringen die Bakterien eine Reihe von erfreulichen Eigenschaften mit, die sie zu einem begehrten cellulären Testobjekt machen. Sie haben einmal eine hohe metabolische Aktivität, vermehren sich also rasch, so daß die Auswirkungen einer Bestrahlung in relativ kurzer Zeit beobachtet werden können. Beispielsweise benötigt ein E. coli-Bacterium für eine Teilung unter optimalen Wachstumsbedingungen etwa 17 min. Die Bakterien können ferner auf einfachen, wohldefinierten Medien gezüchtet werden; falls dies auf festen Nährböden geschieht, entstehen dabei Kolonien, die mit bloßem Auge ausgezählt werden können. Besonders interessant für strahlenbiologische und genetische Experimente ist die Tatsache, daß die Struktur des Bakteriengenoms im Vergleich zu höheren Zellen sehr einfach ist. Allerdings geht diese Einfachheit so weit, daß man fast schon geneigt ist, von einer Ausnahmestellung der Bakterien zu sprechen. Sie besitzen nämlich im Gegensatz zu anderen Zellen keinen Zellkern im klassischen Sinne. Es kann allgemein auch keine Kernmembran nachgewiesen werden, weshalb man die färbbaren DNS-haltigen Regionen, die unter dem Mikroskop ein recht verschiedenartiges Aussehen zeigen können, vorsichtig als Kernäquivalente bezeichnet. Ein Bacterium kann je nach Wachstumsphase und Wachstumsbedingungen mehrere Kernäquivalente besitzen. Die der Zellteilung vorangehende Teilung der Kernäquivalente hat wenig Ähnlichkeit mit dem Mechanismus der Chromosomenverdoppelung in höheren Zellen. Es gibt keinen Spindelapparat, und es erfolgt auch keine Durchmischung der DNS aus den einzelnen Kernäquivalenten einer Bakterienzelle. Trotz dieser phäno-menologischen Abweichungen spricht man besonders bei den Coli-Bak-terien, die bemerkenswert kompakte Kernäquivalente besitzen, von Kernen und sogar von Chromosomen.
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Light is a very important environmental factor that governs many cellular responses in organisms. As a consequence, organisms possess different kinds of light-sensing photoreceptors to regulate their physiological variables and adapt to a given habitat. The cryptochrome/photolyase family (CPF) includes photoreceptors that perform different functions in different organisms. Photolyases repair ultraviolet-induced DNA damage by a process known as photoreactivation using photons absorbed from the blue end of the light spectrum. On the other hand, cryptochromes act as blue-light circadian photoreceptors in plants and Drosophila to regulate growth and development. In mammals, cryptochromes have light-independent functions and are very important transcriptional regulators that act at the molecular level as negative transcriptional regulators of the circadian clock. In this review, we highlight current knowledge concerning the structural and functional relationships of CPF members. This article is protected by copyright. All rights reserved.
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In den Desoxyribonucleinsäuren (DNS)1 der Zellen und der Viren ist die genetische Information enthalten, welche die identische Reproduktion der biologischen Systeme gewährleistet. Neben der DNS kommt bei einer Reihe von Viren auch noch Ribonucleinsäure (RNS) als Informationsträger vor.
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Now that it has been made clear that the earliest protobiont had to possess a genetic mechanism before further evolution could occur, clues to two major questions will be sought as the basis for inheritance is reviewed in this present and the following two chapters. The first of these pertains to the nature of the genetic apparatus that probably existed in the very first forms of life, and the second involves the sequence of events that led to its present state of complexity. Fortunately data are available that indicate a probable series of developments, but to appreciate their significance fully, each aspect of the genetical processes must first be scrutinized. The most logical point for departure is an investigation of deoxyribose nucleic acid (DNA), the central ingredient in prevailing doctrines. Thus, this molecule, its mode of replication, and its organization in living cells are the topics of the present discussion, after some preliminary points have been established.
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Radiobiological studies in bacteria began in 1877 when Downes and Blunt published their observations of the killing of bacteria by sunlight. A voluminous literature has been accumulated since that date, and in a short discussion it is impossible to accomplish more than to mention briefly some aspects of the subject which, hopefully, are of interest.
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Photoreactivation was discovered by chance in 1949 during a study of UV-induced mutagenesis when unexpected results were obtained that could be attributed to a greatly enhanced survival of UV-irradiated Streptomyces griseus conidia after illumination with visible light (38). A similar phenomenon was found for the survival of UV-irradiated bacteriophages in Escherichia coli (11).
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Light is an important environmental signal. An organism survives by its ability to adapt to the conditions of its environment; many organisms are known to respond to light and photoresponsive molecules are widespread in nature. The interaction of light with an enzyme is one of the possible means for biological systems to respond. Light may influence either an increase or decrease in enzyme activity; thus light affects the chemistry of the cell. These processes can be very complex (e.g., photomodulation of chloroplast enzymes) or they can be remarkably simple (e.g., photoactivation of urocanase). Reversion is an essential part of photomodulation.
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Few molecules captivate like DNA. It enthrals scientists, inspires artists, and challenges society. It is, in every sense, a modern icon. A defining moment for DNA research was the discovery of its structure half a century ago. On 25 April 1953, in an article in Nature, James Watson and Francis Crick described the entwined embrace of two strands of deoxyribonucleic acid. In doing so, they provided the foundation for understanding molecular damage and repair, replication and inheritance of genetic material, and the diversity and evolution of species.
Article
Ultraviolet (UV) radiation-induced DNA damage leading to entomopathogenic fungal inactivation is commonly measured by viability counts. Here we report the first quantification of UV-induced cyclobutane pyrimidine dimers (CPD) in DNA of the entomopathogenic fungus, Beauveria bassiana. Changes in the mobility of UV-C irradiated DNA were resolved with CPD specific bacteriophage T4 endonuclease V and alkaline agarose gel electrophoresis. The maximum number of CPD formed in B. bassiana DNA in vitro by UV-C irradiation was 28 CPD/ 10 kb after 720 J/m² dose. The maximum number of CPDs formed in B. bassiana conidiospore DNA irradiated in vivo was 15 CPD/10 kb after 480 J/m² dose and was quantified from conidiospores that were incubated to allow photoreactivation and nucleotide excision repair. The conidiospores incubated for photoreactivation and nucleotide excision repair showed decreased number of CPD/10 kb DNA and a higher percent survival of conidiospore populations than conidiospores not allowed to repair.
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Light‐driven biocatalysis has emerged as a powerful approach to unlock new enzymatic reactivity modes. In this field, flavoenzymes are particularly effective, owing to the presence of a redox‐active cofactor that can act as a photocatalyst. The irradiation with visible light therefore enables new catalytic functions, which complement the natural reactivity repertoire of flavoenzymes. Herein, we provide a comprehensive review of native and promiscuous photoenzymatic activities of flavin‐dependent proteins. In addition, flavoenzyme‐based synergistic systems with an exogenous photoredox catalyst are discussed.
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Damaging DNA is a current and efficient strategy to fight against cancer cell proliferation. Numerous mechanisms exist to counteract DNA damage, collectively referred to as the DNA damage response (DDR) and which are commonly dysregulated in cancer cells. Precise knowledge of these mechanisms is necessary to optimise chemotherapeutic DNA targeting. New research on DDR has uncovered a series of promising therapeutic targets, proteins and nucleic acids, with application notably via an approach referred to as combination therapy or combinatorial synthetic lethality. In this review, we summarise the cornerstone discoveries which gave way to the DNA being considered as an anticancer target, and the manipulation of DDR pathways as a valuable anticancer strategy. We describe in detail the DDR signalling and repair pathways activated in response to DNA damage. We then summarise the current understanding of non-B DNA folds, such as G-quadruplexes and DNA junctions, when they are formed and why they can offer a more specific therapeutic target compared to that of canonical B-DNA. Finally, we merge these subjects to depict the new and highly promising chemotherapeutic strategy which combines enhanced-specificity DNA damaging and DDR targeting agents. This review thus highlights how chemical biology has given rise to significant scientific advances thanks to resolutely multidisciplinary research efforts combining molecular and cell biology, chemistry and biophysics. We aim to provide the non-specialist reader a gateway into this exciting field and the specialist reader with a new perspective on the latest results achieved and strategies devised.
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Light from a lab’s windows and lamps illuminated the path to the discovery of DNA repair.
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A growing world population is demanding food and energy at the highest pace in the history of human kind. Plant biotechnology oriented to sustainable and competitive agriculture should lead a trail of innovation in order to address these emerging needs. The last decade has been characterized by the explosive accumulation of vast amounts of discoveries in the field of molecular biology. These achievements have paved the way for the advent of novel developments in plant biotechnology. Several new tools are being applied for genetic crop improvement every day, based on breakthrough versatile platforms that are increasing effectiveness and speed in the generation of new varieties of crops. The latest achievements are not only adaptations or improvements of modern techniques such as intra- and cis-genesis and accelerated breeding based on transgenics and null-segregants, meganucleases, and zinc finger nucleases; they are also the dawn of new disruptive technologies that are reshaping the paradigm of genetic improvement, as is the case with TALEN and CRISPR/Cas. Sitedirected genome editing is becoming precise, cost-effective, versatile, and fast. These new breeding platforms are leading the way to next generation biotechnology. This chapter discusses the most recent updates and developments of new breeding techniques, paradigmatic achievements, future perspectives, and challenges in the context of plant biotechnology.
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Bacteria are the smallest, autonomous living systems with differentiated metabolic processes and able to reproduce independently. They also have a number of characteristics that make them a favoured radiation-biological cellular test system. They have a high metabolic activity and therefore reproduce rapidly, so that the effect of an irradiation can be observed after a relatively short period. For example, an E. coli bacterium divides about once in every 17 minutes under optimal growth conditions. Bacteria can be grown on well-defined media; if this is solid, colonies that can be counted with the naked eye are formed. The fact that the structure of the bacterial genome is very simple compared with that of higher cells is of particular interest for experiments in radiation biology and genetics. However, it is so simple that it might be considered to be a special case. In contrast to other cells, bacteria do not have a cell nucleus in the classical sense. Moreover, the division of the genetic material preceding normal cell division has few similarities with to the mechanism of chromosome duplication in higher cells; no spindle apparatus can be observed during this process. In spite of these phenomenological differences the terms nuclei and chromosomes are used, especially in the case of coli bacteria in which the genetic material gives the impression of being very compact. Bacteria contain varying numbers of nuclei, depending on their stage and conditions of growth.
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In order to place the different methods used to estimate carcinogenic risk from chemical exposure into context, and to help decide on the best approach to improve this process, it is useful to discuss carcinogenesis with an emphasis on mechanism. Although the mecha nism of action of no carcinogen is completely characterized, the efforts over the last ten years have been very fruitful, and mechanistic explanations of a number of components in the grand design that is carcinogenesis have been described in detail.
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Acute traumatic synovitis of the knee is a sprain of the capsule, and a normal functioning knee should therefore result from treatment in all cases. A trial of six different methods of treatment is reported in order to determine which is the best method in terms of symptom relief and early return to work. In general, if quadriceps exercises are performed, results are similar with bed rest alone, with pressure bandage of the knee or by aspiration of the knee. Rigid immobilisation in a plaster cast should be avoided because this delays recovery.